The invention relates to dairy product capsules comprising an envelope inside which said dairy product is confined, and to a process for manufacturing these capsules.
The coating of yogurt in a dietary polymer (sodium alginate) by the technique of dripping yogurt into alginate solution is already known (Japanese patent application in the name of Meiji Milk Prod. Co. Ltd., published under No. 62-130 645): it is indicated in said document that spherical capsules (yogurt beads) are thus obtained.
However, the yogurt capsules obtained according to said Japanese patent application have many drawbacks which considerably limit their possibilities for industrial and commercial exploitation:
it is difficult to coat a fluid dairy product in capsules: all the examples mentioned in the above-mentioned Japanese patent application recommend using a yogurt whose viscosity is high, greater than 2000 mPaxc2x7s at 10xc2x0 C.;
their alginate envelope, which is readily deformable, does not allow their spherical shape to be maintained. They are also very fragile; they break so easily that their handling, in particular during manufacture and packaging, is made very difficult, if not impossible, at an industrial scale;
they are subject to the phenomenon of syneresis, i.e. the exudation of liquid at the surface of the capsule. This phenomenon results in surface irregularities, and also creates an environment that is favorable to microbial growth, which is detrimental to the storage of the beads.
To overcome these drawbacks, it is proposed, in patent application 62 -130 645, to immerse the capsules, as they are formed, into an aseptic or antiseptic solution or a sugar solution, and to leave them therein in order to preserve their spherical shape.
The Inventors thus set themselves the aim of providing strong, stable dairy product capsules which do not need to be immersed in a storage solution, and which are also found by consumers to have a pleasant mouthfeel, and investigated coating polymers which would allow this aim to be achieved.
They have thus found that the selection of coating polymers on the basis of their breaking force makes it possible to obtain capsules that have the desired properties.
One subject of the present invention is thus a capsule comprising an envelope comprising at least one polymer for dietary use, which is reactive with multi-valent ions, inside which is confined a dairy product, characterized in that said capsule has a breaking force of greater than 0.5 N and preferably between 0.5 N and 1.5 N.
For the purposes of the present invention, the expression xe2x80x9cpolymer which is reactive with multivalent ionsxe2x80x9d means a polymer for dietary use which can react chemically with multivalent ions (in the present case, these are ions which have lost more than one electron) to form a crosslinked network (irreversible chemical crosslinking) in the form of a gel. In particular, such polymers comprise guluronic, galacturonic or glucuronic units, more generally uronic units, allowing the chelation of multivalent ions, in particular calcium ions which are present in large amount in dairy products.
Polymers for dietary use which may be used to prepare capsules in accordance with the invention include, for example, alginates, gellans and pectins, or mixtures of these polymers.
The capsules in accordance with the invention advantageously comprise at least 40%, preferably at least 45% and advantageously at least 60%, by weight of dairy product relative to the total weight of the capsule.
The dairy product encapsulated in the polymer envelope for dietary use described above may be a fermented or unfermented dairy product, and may be chosen in particular from yogurts, drinking yogurts, fermented milks, fromages frais, dessert creams and/or dairy mousses. Its texture may be very fluid (dairy product such as a drinking yogurt) or viscous (dairy product such as a stirred yogurt).
The capsules in accordance with the invention are prepared by placing the dairy product to be encapsulated in contact with a bath comprising, in aqueous solution, at least one polymer for dietary use which is reactive with multivalent ions as defined above. The capsules formed are then recovered and may optionally be rinsed and then dried.
Depending on the nature of the dairy product which it is desired to encapsulate, two main variants of the process for preparing the capsules in accordance with the invention may be carried out.
According to a first variant, the placing in contact is carried out by dripping the dairy product to be encapsulated into the bath of dietary polymer.
To obtain capsules having the desired properties, the polymer which will be chosen in this case is one which has, as an aqueous 1% solution, a viscosity (measured at 25xc2x0 C. and at 60 rpm) of less than 200 mPaxc2x7s and preferably less than 100 mPaxc2x7s.
Said polymer is advantageously selected from the group consisting or:
highly gelling alanates with a molecular weight of less than or equal to 100 000 (commonly referred to as depolymerized alginates); these alginates are preferably selected from the group consisting of sodium alginates and potassium alginates;
weakly acetylated gellans, and
pectins with a degree of esterification of less than or equal to 20.
For the purposes of the present invention, the expression xe2x80x9chighly gelling xe2x80x9d means alginates whose guluronic acid content is greater than 50%, and the expression xe2x80x9cweakly acetylatedxe2x80x9d means gellans whose maximum degree of substitution with acetyl groups is 0.03. As regards the degree of esterification of pectins, this corresponds to the percentage of galacturonic units of the pectins which bear a methoxyl group.
By way of example of implementation of this first variant of the process in accordance with the invention, the drops of dairy product may be formed using a rigid tube, the aperture diameter of which governs the diameter of the drops (typically from 2 to 15 mm) and which is located a few centimeters above the bath, for example 5-10 cm above it, the drop height of the drops being adjusted so that the dairy product fully enters the bath and so that the drops have a substantially spherical shape. To do this, the viscosity of the bath should be relatively low, preferably less than 200 mPaxc2x7s at 50 rpm.
The dairy product is advantageously at a temperature of from 4 to 10xc2x0 C. and the bath is at a temperature of from 5 to 50xc2x0 C. approximately. However, the bath temperature should not exceed 45xc2x0 C. in the event that the dairy product is a yogurt, so as not to degrade the bacteria present in the yogurt.
The drops of dairy product are maintained in the bath for a time which is sufficient for a film of gel to form around these drops, by diffusion of the multivalent ions, in particular of the calcium ions present in the dairy product, this gel film being rigid enough to allow the capsules thus formed to be handled. The thickness of this gel film is typically from 0.1 to 0.5 mm and is set by the time of immersion in the bath (from 2 to 20 minutes approximately).
According to a second variant, the placing in contact is carried out by coextruding the dairy product with a solution of said polymer for dietary use. This variant allows the use of polymer solutions of high viscosity for which the technique of dripping the dairy product into the polymer solution can no longer be used. The viscosity of these solutions may be greater than 200 mPaxc2x7s.
Any one of the coextrusion techniques that are known per se for encapsulating food products, in particular pasty food products, may be used. By way of example, mention will be made of the techniques disclosed in patent DE 3 432 923, in international patent application WO 92/14544, in patent DE 2 402 415 or in the book: Microcapsule Processing and Technology, Marcel Dekker, Inc., Ch. 7, 59-63 (1979).
A jacketed tube is used: the dairy product is conveyed in the center, and the solution comprising at least one polymer for dietary use which is reactive with multivalent ions is conveyed at the periphery. Once they leave the inner tube, the drops of dairy product are immediately recovered from the polymer solution and are then introduced into a calcium chloride solution for a time which is sufficient for the gelation reaction to take place and for the envelope of the dairy product capsules to be strong enough to allow them to be handled.
The thickness of the envelope depends on the feed rates in the two tubes and on the respective viscosities of the dairy product and of the polymer solution.
In order to carry out this variant, a polymer solution for dietary use whose viscosity when it is used is about 1100-1200 mPaxc2x7s (measured at 25xc2x0 C. and at 64 sxe2x88x921) is used, such a solution being runny and coating and spreading uniformly over the yogurt drop.
The polymer used is a polymer which is reactive with multivalent ions, chosen from highly gelling alginates, gellans and pectins with a degree of esterification of less than or equal to 20.
Whether the coextrusion technique or the drip technique is used, the polymer solution also advantageously comprises at least one compound selected from the group consisting of plasticizers, sugars, multivalent-ion sequestrants and water-retention agents.
The plasticizer is preferably selected from the group consisting of weakly gelling alginates with a molecular weight of less than or equal to 100000, pectins with a degree of esterification of between 20 and 50, sorbitol, glycerol, maltodextrins and polyols.
The expression xe2x80x9cweakly gelling alginatesxe2x80x9d means alginates whose content of mannuronic acid, this moiety being unreactive with multivalent ions, is greater than 50%.
In a particularly advantageous manner, the presence of at least one plasticizer makes it possible to soften the network formed by the polymer for dietary use with the multivalent ions and thus allows the envelope to melt more satisfactorily in the mouth when it is consumed.
The plasticizer also prevents contraction of the film of polymer for dietary use which is formed and thus further limits the phenomenon of syneresis.
The optional presence of sugar ensures better dispersion of the macromolecules of polymer for dietary use during the preparation of the solution and allows the density of this solution to be adjusted; in addition, it modifies the taste of the gel constituting the envelope of the capsules.
The presence of a multivalent-ion sequestrant makes it possible to trap the excess multivalent ions which contribute toward the phenomenon of syneresis; the multivalent-ion sequestrant is preferably a calcium-ion sequestrant selected from the group consisting of citrates, phosphates, pyrophosphates and metaphosphates. Non-limiting examples which may be mentioned include tetrasodium pyrophosphate (Na4P2O7), sodium hexametaphosphate (Na5(PO3)6) and sodium citrate (C3H4(OH)(COONa)3). As a variant, the sequestrant is present in the dairy product rather than in the polymer solution.
The presence of a water-retention agent makes it possible to limit the syneresis. Such an agent is preferably selected from the group consisting of carob and guar, these compounds being galactomannans extracted from the albumin of legume seeds.
When a water-retention agent is present in the case of capsules formed by the technique of dripping into the bath, said bath is maintained at a temperature which is sufficient to lower its viscosity to a value below 200 mPaxc2x7s; a suitable temperature is, for example, from 30 to 45xc2x0 C.
The polymer solution advantageously comprises (expressed as percentages by weight relative to its total volume):
a) between 0.5% and 5% of polymer for dietary use which is reactive with multivalent ions;
b) between 0 and 10% of plasticizer;
c) between 0 and 2% of sequestrant; and
d) between 0 and 2% and preferably between 0.4% and 2% of water-retention agent.
It may also contain between 0 and 20% of sugar.
According to one preferred embodiment of the process according to the invention, the step of recovering the capsules formed is followed by at least one rinsing of said capsules with deionized and/or sugary water, to remove the traces of non-crosslinked polymer remaining at the surface, thus preventing the reaggregation of the capsules after they have been packaged. For example, three successive rinsings may be carried out, followed by draining the capsules appropriately before they are packaged.
According to another preferred embodiment of the process according to the invention, the rinsing is followed by a step of drying said capsules. Such a drying operation makes it possible to evaporate off the water which is exuded at the surface of the capsules after they have been manufactured, and thus to eliminate any subsequent phenomenon of syneresis. It may be carried out, for example, by placing the capsules in contact with a flow of air for 30 minutes to 5 hours, for example at 4xc2x0 C. (for example in a ventilated refrigerator).
The capsules which may be obtained by one or other of the variants of the process described above constitute preferred embodiments of the present invention.
The envelope of these capsules advantageously comprises, relative to the total dry weight of its various constituents:
a) between 10% and 100% by weight of polymer for dietary use which is reactive with multivalent ions;
b) between 0 and 90%, preferably between 0.5% and 10%, and advantageously at least 1% by weight of plasticizer;
c) between 0 and 30% by weight of multivalent-ion sequestrant;
d) between 0 and 50% of water-retention agent.
The capsules according to the present invention make it possible in particular to coat a fluid dairy product, such as a drinking yogurt or a fluid dessert cream. In addition, they are not particularly fragile and are thus easy to handle during industrial manufacture. These capsules may then be stored without further modification, without the need for a storage solution; they keep their spherical shape, and virtually only a small amount of syneresis is observed, which does not harm the storage.
In addition, the mouthfeel of the capsules in accordance with the invention is very pleasant. Unlike the capsules disclosed in Japanese patent application 62-130 645, the capsules in accordance with the invention are crunchy and release the yogurt, thus producing a sensation of freshness which consumers find very pleasant.